(1) Field of the Invention
The present invention relates to the prevention of the unauthorized operation of equipment and particularly to impeding or precluding theft of motor vehicles. More specifically, this invention is directed to an enabling/disabling device for association with electrically actuated machinery and especially to security apparatus which may be employed to render the starting system of a motor vehicle inoperative. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well-suited for preventing the unauthorized operation of vehicles having engines which are started by means of an electrically actuated started system. An example of the operating environment for the present invention, accordingly, is an automobile having an electrically operated starter motor. For a number of reasons, it is desirable to employ an interlock system which permits the engine of a motor vehicle to be started only by authorized personnel and/or by an individual whose reflexes have not been impaired by alcohol or narcotics.
Numerous techniques for selectively disabling and enabling the ignition and/or starting circuit of motor vehicles have previously been suggested. Thus, by way of example, ignition circuit disabling switches have been secreted at various places in an automobile, the location of the switches being known only to the owner/operator. It has also been proposed to employ keypads and associated logic circuitry which would enable all or parts of the vehicle's electrical system only when a multi-digit code was entered via the keypad within a predetermined time period. A further prior art approach to rendering a motor vehicle theft-resistant has been to employ a dual system wherein a first coded key was utilized to enable the vehicle electrical system whereupon the regular ignition key could be employe to start the vehicle.
The prior art systems for preventing unauthorized vehicle operation have often been characterized by rather complex electronics which rendered the systems expensive, difficult to install and of somewhat suspect reliability. The prior systems have also been plagued by inoperability due to a susceptibility to vibration induced damage and/or the inability to withstand the temperatures extremes to which they have been subjected. As an additional disadvantage of prior art systems, they have either been exceedingly difficult or impossible to by-pass by the owner/operator. Accordingly, when in an environment such as a public parking garage or a repair shop, where it was necessary to leave a key to permit the vehicle to be moved, it became necessary to inform the attendant of the details of the enabling/disabling system, i.e., the code, location of hidden switch, etc. The necessity of revealing such information, of course, compromises the security of the system.